WASHINGTON — A key al-Qaida operative returned to Pakistan by the CIA after he gave the U.S. information that eventually led to the location of Osama bin Laden has since rejoined al-Qaida, U.S. officials say.

The agency returned Hassan Ghul to Pakistan not long after the CIA closed its remaining secret prisons in Eastern Europe in 2006.

The CIA had been given assurances that Ghul, a native of Pakistan, would not go free. But Pakistan failed to keep its word. Ghul was let go and later rejoined al-Qaida, angering the CIA officers who worked so hard to take him off the battlefield, according to former and current U.S. intelligence officials.

Pakistan's decision to free Ghul is yet another troubling revelation at a time when the U.S. is rethinking its relationship with Pakistan and whether it can be a trusted ally in fighting terrorism. Members of Congress have talked about ending aid to Pakistan after bin Laden was found inside Pakistan, hiding out in an urban area not far from a military garrison. Last week, CIA Director Leon Panetta confronted Pakistan's intelligence service about tipping off militants running bomb factories aimed at killing U.S. soldiers in Afghanistan.

Ghul's return to Pakistan also raises questions about how the Bush administration, which was committed to keeping arguably less dangerous detainees locked up at the U.S. prison at Guantanamo Bay, Cuba, could hand over the man who provided the key information about bin Laden's trusted courier, intelligence that in May led to bin Laden's death at the hands of U.S. commandos.

The move frustrated former CIA officers, who at the time believed Ghul should have been moved to Guantanamo along with 14 other high-value detainees like Abu Zubaydah, a major al-Qaida facilitator, and Khalid Sheikh Mohammed, the mastermind of the 9/11 attacks.

A U.S. official said Pakistan made promises that it would hold Ghul, only to let him go and re-establish contact with al-Qaida. A senior Pakistani intelligence official said he had no information about Ghul.

The officials spoke on condition of anonymity because details about Ghul's case remain classified.

Former CIA officials say Ghul was part of Zubaydah's clandestine network of moneymen and couriers. He was well-known to the CIA before the 9/11 attacks. The CIA had been pressing Pakistan to arrest Ghul for years and later learned after 9/11 he had been hiding at safe houses in the Lahore area belonging to the terrorist group, Lashkar-e-Taiba, which was behind the 2008 attacks in Mumbai, India.

But Pakistan's spy service, the ISI, refused to pick up Ghul.

When the CIA figured out that Ghul was traveling to meet with al-Qaida operatives who had gone to Iraq after the 2003 invasion to fight the U.S., the agency decided to act. In a joint operation with the Kurds, Ghul was nabbed in northern Iraq in January 2004, former CIA officials said. Pakistan was furious when it learned the CIA had Ghul and pressed the U.S. to return him.

Instead, Ghul was taken to Bagram Air Base in Afghanistan but was later removed over questions about whether the transfer was legal, former CIA officials said. Ghul then was taken to a CIA "black site" — a secret prison — in Eastern Europe and provided crucial information about bin Laden's most trusted courier before he was exposed to harsh interrogation techniques. Ghul's information later allowed the CIA to realize that finding the courier probably would lead to bin Laden.

Ghul also provided key information about the whereabouts of terrorists in Pakistan's lawless tribal areas, the officials said. He provided other precise information as well.

"He was very useful," a former CIA officer said.

Former CIA officials said in the rush to close the secret prisons, the U.S. was looking for ways to get rid of some of the remaining two dozen or so detainees in the agency's now-defunct interrogation and detention program. With Pakistan offering to take Ghul, U.S. officials figured they could also build some good will by giving him back, and the CIA had the ISI's pledge that he wouldn't go free.

It's not clear why Pakistan wanted Ghul back so badly, but former CIA officers who targeted Ghul said he had ties to the Lashkar-e-Taiba terror group, which had the backing of ISI.

Little is known about Ghul's movements after he was sent back to Pakistan. At an undisclosed location in Pakistan, Ghul talked with a British detainee named Rangzieb Ahmed who was held in an adjacent cell. Ghul told Ahmed that he had been held in a secret CIA location for 2 1/2 years and had also passed through Morocco.

Ahmed said the last time he saw Ghul was in January 2007.

Copyright 2011 The Associated Press. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.

Video: Pakistan arrests CIA's bin Laden informants

Closed captioning of: Pakistan arrests CIA's bin Laden informants

>>>is yet another twist to report tonight involving
bin laden
's death, it's once again creating a lot of tension in the relationship, already troubled between
pakistan
and the u.s. for that, we go to our chief
foreign affairs
correspondent
andrea mitchell
.

>>good evening, brian.
pakistan
's powerful military has now erected five cia informants including an army major who helped track down
bin laden
. this is despite the fact that a parade of top u.s. officials have been going to islamabad. all pleading with islamabad and reading the
riot act
to them really for failing to cooperate against terrorists. they also say that
pakistan
's terrorists are costing american lives. this is because that ieds are made in
pakistan
, panetta even showed the pakistanis satellite photos of these bomb facilities in
pakistan
, demanded that they be raided, two days later, somebody must have tipped them off. and the terrorists fled.

An aerial view shows the residential area of Abbottabad, Pakistan, where Osama bin Laden was found and killed by U.S. commandos.
(Asif Hassan / AFP - Getty Images)
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A general view of the town of Abbottabad, May 6. Bin Laden was living in a large house close to a military academy in this garrison town, a two-and-a-half hour-drive from the capital, Islamabad.
(Khaqan Khawer / EPA)
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Supporters of Pakistani religious party Jamaat-e-Islami rally to condemn the killing of bin Laden, in Abbottabad on May 6.
(Aqeel Ahmed / AP)
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A Pakistani woman photographs her daughter on May , at a gate of the compound where bin Laden was caught and killed.
(Aqeel Ahmed / AP)
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School girls pass by armed Pakistani policemen guarding the sealed entrance to the compound in Abbottabad, May 5, in which bin Laden had been living.
(MD Nadeem / EPA)
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A Pakistani police officer gestures at a checkpoint along a road leading to a house where bin Laden was captured and killed in Abbottabad. Area residents were still confused and suspicious about bin Laden's death, which took place before dawn on Monday.
(Anjum Naveed / AP)
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Part of a damaged U.S. MH-60 helicopter lies the compound. The helicopter was destroyed by U.S. forces after a mechanical failure left it unable to take off.
(Reuters)
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A still image from video obtained by ABC News shows blood stains in the interior of the house where bin Laden was killed.
(ABC News via Reuters)
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Aerial views released by the Department of Defense show the area in Abbottabad in 2004, left, before the house was built, and in 2011, right.
(Department of Defense via Reuters)
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Boys collect pieces of metal from a wheat field outside bin Laden's house, seen in the background, on May 3. People showed off small parts of what appeared to be a U.S. helicopter that the U.S. says malfunctioned and was blown up by the American team as it retreated.
(Anjum Naveed / AP)
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An image from video seized from the walled compound of al-Qaida leader Osama bin Laden in Abbottabad, and released by the U.S. Department of Defense, shows Osama bin Laden watching TV. He is said to have spent his last weeks in a house divided, amid wives riven by suspicions. On the top floor, sharing his bedroom, was his youngest wife and favorite. The trouble came when his eldest wife showed up and moved into the bedroom on the floor below.
(Department of Defense via AP)
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Editor's note:
This image contains graphic content that some viewers may find disturbing.

Timeline: A timeline of Osama bin Laden's life

Considered enemy No. 1 by the U.S., the Saudi millionaire is the perpetrator behind the Sept. 11, 2001, attacks. Click on key dates to learn more about the founder of al-Qaida, an international terror network.

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